DNA length

Logically, if the answer to either Q1 or Q2 is "yes," then the answer to
Q3 must also be "yes." Indeed, the answer to all three is "yes."
As to Q4, there are in my experience two kinds forces invoked to explain
molecular variation between and within species: selection of one kind or
another, and drift. Furthermore, the determination of what force accounts
for a particular instance of variation is done on a case-by-case basis in
light of the details of the variation in question, and often not without
considerable controversy.
Molecular_evolutionary_genetics by M Nei (1987) is probably a reasonable
starting point for a more detailed exploration of Q4. Apologies if you
were hoping for a simple answer!
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Dan Weinreich email: dmw at mcz.harvard.edu
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Museum of Comparative Zoology Cambridge, MA 02138
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